The present invention relates generally to apparatus for bonding electronic dies to a substrate and more specifically to a multi head bonder.
Inner lead bonders for bonding dies to the leads of a carrier tape can be performed with extreme accuracy since the positioning of the leads on the carrier tape is well controlled. A typical example is U.S. Pat. No. 4,526,646 to Suzuki, et al. wherein the carrier tape 16 has its XY position adjusted with respect to the bond site. Die positioning fingers 43 adjust the .theta. and the X coordinate of the die with respect to table 40. A die defect detection camera 81 is provided at the wafer pick-up station. A die positional pattern detecting camera 83 detects positional deviation in the Y direction. A lead positional pattern detection camera 85 detects the position of the lead pattern at the bond site. The positional deviation of the lead pattern of the carrier tape 16 from the pattern of the die 51 detected by camera 83 is computed. Then, the XY table 31 is driven to adjust the tape carrier with respect to the bond head 10 in die 51 for the computed deviation.
The Suzuki, et al. patent is just one of many patents which illustrate the use of a pair of tools to transport a die in a bonder between three specific stations. In that it uses a pair of tools, each of the tools can operate simultaneously thereby increasing the through-put. This is to be distinguished from a single tool reciprocating along a single path between all the stations as illustrated in FIG. 1 which is a die bonder model "Argus" from Assembly Technologies of Horsham, Pa. Both of these systems are only capable of processing a plurality of dies of the same dimension and characteristics.
In an attempt to further increase the through-put of a die bonder, multiple tools can be used. An example is shown in U.S. Pat. No. 4,372,082 to Harigan, et al. A vacuum shifting head 18 transfers dies 20 from a pallet 8 to a plurality of mounting heads 15 on a turret mounting mechanism 16. As illustrated in FIG. 6, the turret 16 has eight positions from the die receipt position A to the die mounting position E. The die is aligned by claws 124 at position B as illustrated in FIGS. 25-28. At position C, the .theta. of die is adjusted by motor 72 through appropriate gears as illustrated in FIGS. 8 and 20. Actuation for the lowering block 80 at the bonding station is illustrated in the FIGS. 19, 21 and 22. The connection of the vacuum source to the suction pin 44 of mounting 15 is illustrated specifically in FIG. 22. Although this design improves the through-put, it is a specifically designed machine and the use of an expensive turret with additional transfer mechanisms is not economical, nor does it allow adaption to existing machines of the prior art as illustrated in FIG. 1.
Thus, it is an object of the present invention to provide a multi-head die bonding machine which is capable of being used with existing bonders.
Another object of the present invention is to provide a multi-head die bonding system which can replace and be used in the envelope of the drive in reciprocal bonders.
An even further object of the present invention is to provide a die transport system which operates in a unit in a single direction.
A still further object of the present invention is to provide a multi-head die bonding system which includes different tool configurations for different sizes of dies for die kits.
A still even further object of the present invention is to provide a multi-head die bonding system wherein each of the heads are individually programmable to by pass disabled or faulty die heads.
These and other objects are achieved by mounting a plurality of die heads on a conveyor which spaces and moves the heads along a path. An alignment mechanism is provided at each station for aligning the head at a fixed position along the path at the station. A controller controls the conveyor to position the plurality of heads at the stations and controls operation of the heads at the stations. The conveyor includes at least one and preferably two vertically spaced endless flexible belts. The heads are mounted to a flexible mount on the belts. The path includes a die supply station, a bonding station and at least one processing station between the die supply station and the bonding station. The heads are spaced along the conveyor such that more than one head is in the path at a time and preferably one head at each of the stations. The conveyor intermittently moves the heads between the stations and through a fly processing station if one is provided.
The alignment mechanism at each of the stations includes a first and second jaw movable relative to each other and transverse to the path for clamping the heads at a fixed position in two orthogonal directions at the stations. Preferably, the first jaw is stationary and the second jaw, which includes an indenture, is movable. Drivers may be provided at one or more stations for mating with the head to control the orientation of the head at the station. The driver and the movable jaw may be provided on a common carriage for positioning the second jaw and the driver at the station once the head is in place. The driver may raise or lower the head. Another kind of driver would adjust the angular position of the head and may be provided on the carriage or may be movable on a separate carriage. A vacuum source is connected to the individual heads such that the head can rotate relative to the connection for angular positioning of the head about a vertical axis. At least two of the heads are configured for different dies and the controller is programmable for each configuration. Similarly, the controller is programmable to selectively operate or not operate each head at each station.